This invention relates to database systems, and particularly to a method and a system for performing a background copy process during a backup operation.
Data protection functionality is not one of the core components of a database. Functions such as backup and restore are typically provided by additional utilities. In some cases these utilities can be third party products (compared to the database) or can be integrated as part of the database software. These tools are called data protection management (dpm).
These utilities provide functionality to perform consistent backups of the databases and providing the link between the database and the enterprise data backup and recovery servers.
Using these utilities database applications are aware whether a backup of the vital data is performed or not. In case of traditional backup methods via a local area network (LAN) or a storage area network (SAN), backups of the vital data may take a long period of time, e.g. up to several hours. The performance degradation of the database server and thus of the application above is considerable especially for heavily utilized databases.
Also data protection management tools exist which can use copy technologies of storage subsystems to protect vital data (backup/restore). Such a feature makes it possible to create, nearly instantaneously, point-in-time or snapshot copies of entire logical volumes or data sets. Point-in-time, or snapshot, may be best understood as the state of a system at a particular point in time. The term was coined as an analogy to that in photography. It can refer to an actual copy of the state of a system or to a capability provided by certain systems.
One such copy technology is FlashCopy, a brand name of International Business Machines (IBM). This is a feature supported on various IBM storage devices. A utility providing a similar function is branded as ShadowImage by Hitachi Data Systems. Using either utility, the copies are immediately available for both read and write access.
When data is protected using FlashCopy a volume copy of a source to a target volume is performed. This point-in-time copy is then typically made available on another computer system. From there the data is moved to the enterprise data backup and recovery software. The copy of the date is immediately available as soon as the mapping between the source and target volume has been created.
In an asynchronous process the data is then physically copied from the source to the target volume in a background copy process. Since the background copy process accesses the source disks where the actual vital production data resides, to physically copy this date to the target volume, performance degradation of the database occurs. This is considerably less than for traditional backup methods via LAN or SAN but can still be sensed in and impact especially heavily utilized databases.
A database uses utilities to protect its vital data via a data protection management utility. A utility providing data protection mechanisms is termed data protection management or dpm. There are also tools known for monitoring performance of a database. A utility measuring and/or monitoring performance of a database and processing these performance data are termed performance monitoring facility or pmf.
A Service Level Agreement or SLA is part of a service contract where the level of service is formally defined. In practice, the term SLA is sometimes used to refer to the contracted delivery time of the service or performance. By way of example, the performance characteristics can be defined for the database directly, e.g. a maximum input/output wait time. These characteristics can be measured, evaluated and violations reported or actively prevented. The database performance can be influenced by many reasons besides an ongoing background copy process, for instance by network problems, thrashing buffer pool and the like.